A high-power laser diode array has the advantages of having a small volume, high efficiency, a long life and so on, and is widely used in industrial manufacturing. Usually by stacking several bars, the output power of a semiconductor laser device can be increased to fulfill increasingly high requirements of the laser diode device. However, with the limitation of heat dissipation and the thickness of the bars themselves, the periods between two bars during the several bars being stacked cannot be too small, and generally are around 2 mm, and even bigger than 3 mm for the latest high output power bars. And the height of a fast axis collimating lens is above 1.5 mm. Meanwhile, after being collimated by the fast axis collimating lens, the beams along a fast axis direction cannot fill the whole height of the fast axis collimating lens, and generally occupy about 50%˜75% of the whole height of the fast axis collimating lens. So, there are considerable interspaces between the beams outputted by the vertical stack comprising the laser diode array after passing through the fast axis collimating lens.
In this case, appropriate light beam coupling method (that is, beam combining technology) can be adopted to rearrange the beams of adjacent laser diode arrays by using an optical element to decrease the interspaces between, and increase the average luminance of the vertical stack output light beams.
Nowadays, the common beam combining technologies of the semiconductor vertical stack laser device are polarization beam combining technology, wavelength beam combining technology and space beam combining technology.
Polarization beam combining technology, mainly is based on the polarization property of the laser device, to make two-branch lasers with different polarization directions to be combined together and propagated along a same optical path direction, for example, as introduced in the U.S. Pat. No. 6,993,059 B2, by using a wave plate and a polarization coupling prism, the beams of upper half and lower half of the stack are outputted overlapped, usually the polarization beam combining technology is to make two-branch laser beams or laser beam combinations with perpendicular polarization directions to combine with each other, and is always used with other beam combining technologies.
Wavelength beam combining technology, is to combine laser beams with different wavelengths by using optical elements such as a dichroscope, a grating and so on, the power and luminance can be improved effectively, and it's the main developing direction of high-power direct semiconductor laser devices nowadays. However no mater adopting a dichroscope, a volume Bragg grating or a diffraction grating, it will always be limited by the spectrum, different wavelengths need to be independent with each other and enough wavelength spacing need to be kept.
Space combining technology, for example, as introduced in U.S. Pat. No. 6,124,973 by Keming Du et al, is to form a group of laser beams propagating along a same direction by arranging and stacking several semiconductor laser devices in space according to a certain sequence, so a high-power laser output can be gotten. However generally speaking, the space stacking cannot improve the quality of beams, so the high-power laser output gotten from this is generally directly used in the cases with requirements of not high beam quality, such as being used as the pump source of fiber laser and so on. But, to the semiconductor vertical stack, for the height along vertical direction of a light beam is decided by the semiconductor vertical stack laser device itself, so there are obvious spacing between adjacent beams, so to a semiconductor vertical stack laser device, a laser source with high energy density can be gotten by using space beam combining technology. For example as published in a Chinese patent CN102751660A, and for another example as published in a Chinese patent CN103944067A, but with the limitation of the problem of whether the spacing size of the stack and the size of the fast axis facula is matched or not, the spacing in the beams may not be eliminated completely.